Data processing method and system

ABSTRACT

A data processing method when the handover or change appears between systems includes: a Mobility Management network element sends a data forwarding tunnel identifier of a target side processing network element to a user plane anchor network element, obtains a data forwarding tunnel identifier of the user plane anchor network element, and sends the data forwarding tunnel identifier of the user plane anchor network element to a source data forwarding network element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/546,748, filed on Nov. 18, 2014, which is a continuation of U.S.patent application Ser. No. 13/672,307, filed on Nov. 8, 2012, now U.S.Pat. No. 8,908,627, issued on Dec. 9, 2014, which is a continuation ofU.S. patent application Ser. No. 12/371,078, filed on Feb. 13, 2009, nowU.S. Pat. No. 8,325,675, issued on Dec. 4, 2012, which is a continuationof International Patent Application No. PCT/CN2007/070384, filed on Jul.30, 2007. The International Patent Application claims priority toChinese Patent Application No. 200610115381.3, filed on Aug. 15, 2006.The afore-mentioned patent applications are hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates to the field of telecommunications and inparticular to a data processing technique and system.

BACKGROUND OF THE INVENTION

Existing General Package Radio Service (GPRS)/Universal MobileTelecommunications System (UMTS) techniques employ network architecturesimilar to second-generation wireless communication systems, includingUMTS Territorial Radio Access Network (UTRAN), GSM/EDGE Radio AccessNetwork (GERAN), Core Network (CN) and Mobile Station (MS), asillustrated in FIG. 1. The GERAN/UTRAN implements all wireless relatedfunctions, and the CN handles all voice calls and data connections inGPRS/UMTS and implements switching and routing functions with externalnetworks.

Logically the CN can be divided into a Circuit Switched (CS) domain anda Packet Switched (PS) domain, supporting voice and data servicesrespectively.

The CS domain includes nodes such as Mobile Switching Center (MSC)server, Media Gateway (MGW) and Gateway Mobile Switching Centre (GMSC)server. The MSC server transmits control plane data of the CS domain,and implements functions such as mobility management, call control andauthentication encryption; the GMSC server handles call control andmobility control in the control plane for a GMSC; the MGW handlestransmission of user plane data.

The PS domain includes nodes such as Serving GPRS Support Node (SGSN)and Gateway GPRS Support Node (GGSN). The GGSN is an interface tointeract with external networks. Also, as a user plane anchor (i.e. userplane anchor network element) between a GERAN and a UTRAN, the GGSNtransmits data of the user plane. Having a position similar to the MSCserver in the CS domain, the SGSN implements functions such as routingforwarding, mobility management, session management and user informationstorage.

Home Location Registers (HLRs) are used in both the CS domain and the PSdomain to store user subscription information.

In existing 3GPP protocols, user plane processing of UMTS is based on atwo-tunnel mechanism illustrated as in FIG. 2. In UMTS, the user planeprocessing is between a Radio Network Controller (RNC, a network elementof a UTRAN, used to control wireless resources of the UTRAN) and anSGSN, and between an SGSN and a GGSN, over an Iu interface and a Gninterface respectively. For the two-tunnel mechanism, an SGSN handlesboth the user plane and the control plane; therefore control planeprocessing and user plane processing are not separate.

With the introduction of High Speed Packet Access (HSPA) and IPMultimedia Subsystem (IMS), there will be a significant data flow growthin future 3GPP network. At present, in order to improve data processingcapability of UMTS, a new UMTS user plane processing mechanism, i.e.direct-tunnel mechanism, has been proposed. As illustrated in FIG. 2, inthis mechanism, the user plane processing of UMTS is between an RNC anda GGSN, without an SGSN. For the direct-tunnel mechanism, an SGSNhandles functions of the control plane only; therefore control planeprocessing and user plane processing are separate.

Now with reference to FIGS. 3 to 6, the processes of handover or changebetween a GERAN and a UTRAN are illustrated hereinafter.

At present, the process of handing over from a GERAN to a UTRANaccording to the protocol 43.129 is illustrated as in FIG. 3:

step S301: a source Base Station Subsystem (BSS) decides to initiate aPS handover;

step S302: the source BSS sends a PS handover request message to an oldSGSN, i.e. 2G SGSN;

step S303: the 2G SGSN sends a forward relocation request message to anew SGSN, i.e. 3G SGSN;

step S304: the 3G SGSN builds a relocation request message and sends themessage to a target RNC;

step S305: the target RNC sends a relocation request acknowledge messageto the 3G SGSN;

step S306: the 3G SGSN sends a forward relocation response to the 2GSGSN;

step S307: the 2G SGSN receives an IP packet from a GGSN and sends theIP packet to an MS via the source BSS;

step S308: the 2G SGSN forwards the IP packet to the target RNC via the3G SGSN;

step S309: the 2G SGSN sends a PS handover request acknowledge messageto the source BSS;

step S310: the MS sends a handover to UTRAN complete message to thetarget RNC;

step S311: the target RNC sends a relocation complete message to the 3GSGSN;

step S312: the 3G SGSN sends an update PDP context request message tothe GGSN;

step S313: the GGSN returns an update PDP context response message tothe 3G SGSN;

The process of handing over from a UTRAN to a GERAN is illustrated as inFIG. 4:

step S401: a source RNC decides to initiate a PS handover;

step S402: the source RNC sends a relocation request message to an oldSGSN, i.e. 3G SGSN;

step S403: the 3G SGSN sends a forward relocation request message to anew SGSN, i.e. 2G SGSN;

step S404: the 2G SGSN builds a PS handover request message and sendsthe message to a target BSS;

step S405: the target RNC sends a PS handover request acknowledgemessage to the 2G SGSN;

step S406: the 2G SGSN sends a forward relocation response message tothe 3G SGSN;

step S407: the 3G SGSN receives an IP packet from a GGSN and sends theIP packet to an MS via the source RNC;

step S408: the 3G SGSN sends a relocation command message to the sourceRNC;

step S409: the source RNC forwards the IP packet to the 3G SGSN, the 3GSGSN forwards the IP packet to the 2G SGSN, and the 2G SGSN forwards theIP packet to the target BSS;

step S410: the target BSS sends a PS handover complete message to the 2GSGSN;

step S411: the 2G SGSN sends an update PDP context Request message tothe GGSN;

step 412: the GGSN returns an update PDP context response message to the2G SGSN;

At present, the process of changing from a GERAN to a UTRAN according tothe protocol 23.060 is illustrated as in FIG. 5:

step S501: an MS decides to perform an inter-system change;

step S502: the MS sends a routing area update request message to a newSGSN, i.e. 3G SGSN;

step S503: the 3G SGSN sends an SGSN context request message to an oldSGSN, i.e. 2G SGSN, to obtain user context;

step S504: the 2G SGSN returns an SGSN context response message to the3G SGSN, and carries the user context information in the contextresponse message;

step S505: the 3G SGSN sends an SGSN context acknowledge message to the2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive datapackets;

step S506: the 2G SGSN duplicates a buffered data packet and forwards tothe 3G SGSN;

step S507: the 3G SGSN sends an update PDP context request message to aGGSN;

step S508: the GGSN returns an update PDP context response to the 3GSGSN;

step S509: the 3G SGSN returns a routing area update accept message tothe MS;

step S510: the MS returns a routing area update complete message to the3G SGSN;

step S511: the MS sends a service request message to the 3G SGSN;

step S512: Radio Access Bearer (RAB) Assignment procedure is performedbetween the 3G SGSN and an RNC, thereby establishing a RAB;

At present, the process of changing from a UTRAN to a GERAN according tothe protocol 23.060 is illustrated as in FIG. 6:

step S601: an MS decides to perform an inter-system change;

step S602: the MS sends a routing area update request message to a newSGSN, i.e. 2G SGSN;

step S603: the 2G SGSN sends an SGSN context request message to an oldSGSN, i.e. 3G SGSN, to obtain user context;

step S604: the 3G SGSN sends an SRNS context request message to a sourceRNC;

step S605: the source RNC returns an SRNS context response message tothe 3G SGSN, stops sending downlink data to the MS, and buffers thedata;

step S606: the 3G SGSN returns an SGSN context response message to the2G SGSN, and carries the user context information in the contextresponse message;

step S607: the 2G SGSN sends an SGSN context acknowledge message to the3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive datapackets;

step S608: the 3G SGSN sends an SRNS data forward command to the sourceRNC, the source RNC duplicates a buffered data packet and forwards tothe 3G SGSN;

step S609: the 3G SGSN forwards the data packet to the 2G SGSN

step S610: the 2G SGSN sends an update PDP context request message to aGGSN;

step S611: the GGSN returns an update PDP context response to the 2GSGSN;

step S612: the 2G SGSN returns a routing area update accept message tothe MS;

step S613: the MS returns a routing area update complete message to the2G SGSN;

In the processes as illustrated in FIGS. 3 to 6, the user plane dataprocessing when a handover or change from a GERAN to a UTRAN takes placeis that, a 3G SGSN forwards data that are forwarded to by a 2G 3GSN to atarget RNC; and the user plane data processing when a handover or changefrom a UTRAN to a GERAN takes places is that, a 3G SGSN forwards datathat is forwarded to by a source RNC to a 2G SGSN. However, in adirect-tunnel mechanism where a 3G SGSN no longer performs user planedata processing, data forwarding cannot be done via a 3G SGSN.Therefore, the existing data processing method when a handover or changebetween a GERAN and a UTRAN takes place does not fit the direct-tunnelmechanism.

SUMMARY OF THE INVENTION

A data processing method and system are provided by the presentinvention, in order to implement data forwarding in a direct-tunnelmechanism when a handover or change between a 2G system and a 3G systemtakes place.

An embodiment of the present invention provides a data processing methodwhich is performed by a Mobility Management Entity (MME). The MMEinforms a User Plane Entity (UPE) of a data forwarding tunnel identifierof a 2G Serving GPRS Support Node (SGSN), obtains a data forwardingtunnel identifier of the UPE, and informs a Long Term Evolution (LTE)access network of the data forwarding tunnel identifier of the UPE. Thedata forwarding tunnel identifier of the UPE is used by the LTE accessnetwork to forward data to the UPE, and the data forwarding tunnelidentifier of the 2G SGSN is used by the UPE to forward the datareceived from the LTE access network to the 2G SGSN.

Another embodiment of the present invention provides a data processingmethod which is performed by a Serving GRPS Support Node (SGSN). TheSGSN informs a User Plane Entity (UPE) of a data forwarding tunnelidentifier of a Long Term Evolution (LTE) access network, obtains a dataforwarding tunnel identifier of the UPE and informs a source RadioNetwork Controller (RNC) of the data forwarding tunnel identifier of theUPE. The data forwarding tunnel identifier of the UPE is used by thesource RNC to forward data to the UPE, and the data forwarding tunnelidentifier of the LTE access network is used by the UPE to forward thedata received from the source RNC to the LTE access network.

A further embodiment of the present invention provides a MobilityManagement Entity (MME). The MME includes a receiver and a sender. Thereceiver is configured to receive a data forwarding tunnel identifier ofa User Plane Entity (UPE) from the UPE. The sender is configured to sendthe data forwarding tunnel identifier of the UPE to a 2G Serving GPRSSupport Node (SGSN), and send a data forwarding tunnel identifier of aLong Term Evolution (LTE) access network to the UPE. The data forwardingtunnel identifier of the UPE is used by the 2G SGSN to forward data tothe UPE, and the data forwarding tunnel identifier of the LTE accessnetwork is used by the UPE to forward the data received from the 2G SGSNto the LTE access network.

A still further embodiment of the present invention provides a MobilityManagement Entity (MME). The MME includes a receiver and a sender. Thereceiver is configured to receive a data forwarding tunnel identifier ofa User Plane Entity (UPE) from the UPE. The sender is configured to:send the data forwarding tunnel identifier of the UPE to a Long TermEvolution (LTE) access network, and send a data forwarding tunnelidentifier of a 2G Serving GPRS Support Node (SGSN) to the UPE. The dataforwarding tunnel identifier of the UPE is used by the LTE accessnetwork to forward data to the UPE, and the data forwarding tunnelidentifier of the 2G SGSN is used by the UPE to forward the datareceived from the LTE access network to the 2G SGSN.

With the data processing methods in the direct-tunnel mechanism when ahandover or change between a GERAN and a UTRAN takes place, a GGSN canbuffer data forwarded by a source data forwarding network element andthen send the data to a target side processing network element;alternatively, the GGSN can send the data forwarded by the source dataforwarding network element directly to the target side processingnetwork element. The problem that the data processing method in theconventional art is not applicable in the direct-tunnel mechanism issolved and normal forwarding of service data in the direct-tunnelmechanism when a handover or change between a GERAN and a UTRAN takesplace is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates network architecture of GPRS/UMTS;

FIG. 2 illustrates user plane processing in the conventional art;

FIG. 3 is a flow chart of a data processing method when a handover froma GERAN to a UTRAN takes place according to the protocol 43.129;

FIG. 4 is a flow chart of a data processing method when a handover froma UTRAN to a GERAN takes place according to the protocol 43.129;

FIG. 5 is a flow chart of a data processing method when a change from aGERAN to a UTRAN takes place according to the protocol 23.060;

FIG. 6 is a flow chart of a data processing method when a change from aUTRAN to a GERAN takes place according to the protocol 23.060;

FIG. 7 is a flow chart of a data processing method when a handover froma GERAN to a UTRAN takes place according to a first embodiment of thepresent invention;

FIG. 8 is a flow chart of a data processing method when a handover froma UTRAN to a GERAN takes place according to a first embodiment of thepresent invention;

FIG. 9 is a flow chart of a data processing method when a change from aGERAN to a UTRAN takes place according to a first embodiment of thepresent invention;

FIG. 10 is a flow chart of a data processing method when a change from aUTRAN to a GERAN takes place according to a first embodiment of thepresent invention;

FIG. 11 illustrates network architecture of an evolved packet corenetwork in the conventional art;

FIG. 12 is a flow chart of a data processing method when a handover froma GERAN to a UTRAN takes place according to a second embodiment of thepresent invention;

FIG. 13 is a flow chart of a data processing method when a handover froma UTRAN to a GERAN takes place according to a second embodiment of thepresent invention;

FIG. 14 is a flow chart of a data processing method when a change from aGERAN to a UTRAN takes place according to a second embodiment of thepresent invention;

FIG. 15 is a flow chart of a data processing method when a change from aUTRAN to a GERAN takes place according to a second embodiment of thepresent invention;

FIG. 16 is a flow chart of a data processing method when a handover froma GERAN to a UTRAN takes place according to a third embodiment of thepresent invention;

FIG. 17 is a flow chart of a data processing method when a handover froma UTRAN to a GERAN takes place according to a third embodiment of thepresent invention;

FIG. 18 is a flow chart of a data processing method when a change from aGERAN to a UTRAN takes place according to a third embodiment of thepresent invention;

FIG. 19 is a flow chart of a data processing method when a change from aUTRAN to a GERAN takes place according to a third embodiment of thepresent invention; and

FIG. 20 is a structural diagram of a data processing system provided inan embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will be described indetails hereinafter with reference to the drawings.

In the specification multiple embodiments of data processing method areprovided. A first method is described hereinafter. The method includes:when a change or handover from a GERAN to a UTRAN takes place, a 2G SGSNforwards a data packet to a GGSN, and the GGSN forwards the data packetto a target RNC; when a handover from a UTRAN to a GERAN takes place, asource RNC forwards a data packet to a GGSN, the GGSN forwards the datapacket to a 2G SGSN, and the 2G SGSN forwards the data packet to atarget BSS.

Now refer to FIG. 7.

As illustrated in FIG. 7, a data processing method when a handover froma GERAN to a UTRAN takes place includes:

step S701: a source BSS decides to initiate a handover;

step S702: the source BSS sends a handover request message to an oldSGSN, i.e. 2G SGSN;

step S703: the 2G SGSN sends a forward relocation request message to anew SGSN, i.e. 3G SGSN;

step S704: the 3G SGSN builds a relocation request message, and sendsthe message to a target RNC;

step S705: the target RNC sends a relocation request acknowledgedmessage to the 3G SGSN;

step S706: the 3G SGSN sends an update PDP context request message to aGGSN, to request to change user plane routing from the GGSN to the 3GSGSN;

step S707: the GGSN returns an update PDP context response to the 3GSGSN;

step S708: the 3G SGSN sends a forward data request to the GGSN, torequest the GGSN to assign a data forwarding tunnel for data forwarding;

step S709: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel and carries the data forwarding tunnel identifier in the responsemessage to the 3G SGSN, the data forwarding tunnel identifier includesIP address and TED (Tunnel End Point Identifier);

step S710: the 3G SGSN sends a forward relocation response message tothe 2G SGSN, a data forwarding tunnel identifier carried in the messageis the data forwarding tunnel identifier of the GGSN;

step S711: the 2G SGSN receives a data packet from the GGSN, and sendsthe data packet to an MS via the source BSS;

step S712: for data of a lossless service, the 2G SGSN forwards the datapacket to the GGSN according to the data forwarding tunnel identifiercarried in the forward relocation response message sent by the 3G SGSN,the GGSN buffers the data packet after receiving the data packetforwarded by the 2G SGSN;

step S713: the 2G SGSN sends a handover request acknowledge message tothe source BSS;

step S714: the MS sends a handover to UTRAN complete message to thetarget RNC;

step S715: the target RNC sends a relocation complete message to the 3GSGSN;

step S716: the 3G SGSN sends an update context request message to theGGSN;

step S717: the GGSN returns an update context response message to the 3GSGSN;

step S718: the GGSN forwards the buffered forwarded data packet to thetarget RNC.

Now with reference to FIG. 8, a data processing method when a handoverfrom a UTRAN to a GERAN takes place includes:

step S801: a source RNC decides to initiate a handover;

step S802: the source RNC sends a relocation request message to an oldSGSN, i.e. 3G SGSN;

step S803: the 3G SGSN sends a forward relocation request message to anew SGSN, i.e. 2G SGSN;

step S804: the 2G SGSN builds a handover request message, and sends themessage to a target BSS;

step S805: the target BSS sends a handover request acknowledged messageto the 2G SGSN;

step S806: the 2G SGSN sends a forward relocation response message tothe 3G SGSN;

step S807: the 3G SGSN sends a forward data request to a GGSN, torequest the GGSN to assign a data forwarding tunnel for data forwarding;

step S808: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel and carries the data forwarding tunnel identifier in the responsemessage to the 3G SGSN;

step S809: the 3G SGSN receives a data packet from the GGSN, and sendsthe data packet to an MS via the source RNC;

step S810: the 3G SGSN sends a relocation command message to the sourceRNC, a data forwarding tunnel identifier carried in the message is thedata forwarding tunnel identifier of the GGSN;

step S811: for data of a lossless service, the source RNC forwards thedata packet to the GGSN according to the data forwarding tunnelidentifier carried in the relocation command message sent by the 3GSGSN, the GGSN buffers the received data packet;

step S812: the target BSS sends a handover complete message to the 2GSGSN;

step S813: the 2G SGSN sends an update context request message to theGGSN;

step S814: the GGSN returns an update context response message to the 2GSGSN;

step S815: the GGSN forwards the buffered forwarded data packet to the2G SGSN.

Now with reference to FIG. 9, a data processing method when a changefrom a GERAN to a UTRAN takes place includes:

step S901: an MS decides to initiate an intersystem change;

step S902: the MS sends a routing area update request message to a newSGSN, i.e. 3G SGSN;

step S903: the 3G SGSN sends an SGSN context request message to an oldSGSN, i.e. 2G SGSN, to obtain user context;

step S904: the 2G SGSN returns an SGSN context response message to the3G SGSN, and carries the user context information in the message;

step S905: the 3G SGSN sends an update PDP context request message to aGGSN, to request to change user plane routing from the GGSN to the 3GSGSN;

step S906: the GGSN returns an update PDP context response to the 3GSGSN;

step S907: the 3G SGSN sends a forward data request message to the GGSN,to request the GGSN to assign a data forwarding tunnel for dataforwarding;

step S908: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel, and carries the data forwarding tunnel identifier in theresponse message to the 3G SGSN;

step S909: the 3G SGSN sends an SGSN context acknowledge message to the2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive datapackets, a data forwarding tunnel identifier carried in the message isthe data forwarding tunnel identifier of the GGSN;

step S910: the 2G SGSN duplicates a buffered data packet and forwards tothe GGSN according to the data forwarding tunnel identifier carried inthe SGSN context acknowledge message sent by the 3G SGSN, the GGSNbuffers the received forwarded data packet;

step S911: the 3G SGSN returns a routing area update accept message tothe MS;

step S912: the MS returns a routing area update complete message to the3G SGSN;

step S913: the MS returns a service request message to the 3G SGSN;

step S914: RAB assignment procedure is performed between the 3G SGSN andan RNC, thereby establishing RAB;

step S915: the 3G SGSN sends an update context request message to theGGSN;

step S916: the GGSN returns an update context response message to the 3GSGSN;

step S917: the GGSN forwards the buffered forwarded data packet to thetarget RNC.

Now with reference to FIG. 10, a data processing method when a changefrom a UTRAN to a GERAN takes place includes:

step S1001: an MS decides to initiate an intersystem change;

step S1002: the MS sends a routing area update request message to a newSGSN, i.e. 2G SGSN;

step S1003: the 2G SGSN sends an SGSN context request message to an oldSGSN, i.e. 3G SGSN, to obtain user context;

step S1004: the 3G SGSN sends an SRNS context request message to asource RNC;

step S1005: the source RNC returns an SRNS context response message tothe 3G SGSN, stops sending downlink data to the MS, and buffers thedata;

step S1006: the 3G SGSN returns an SGSN context response message to the2G SGSN, and carries the user context information in the message;

step S1007: the 2G SGSN sends an SGSN context acknowledge message to the3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive datapackets;

step S1008: the 3G SGSN sends a forward data request to a GGSN, torequest the GGSN to assign a data forwarding tunnel for data forwarding;

step S1009: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel, and carries the data forwarding tunnel identifier in theresponse message to the 3G SGSN;

step S1010: the 3G SGSN sends an SRNS data forward command to the sourceRNC, a data forwarding tunnel identifier carried in the message is thedata forwarding tunnel identifier of the GGSN, the source RNC duplicatesa buffered data packet and forwards to the GGSN, the GGSN buffers theforwarded data packet;

step S1011: the 2G SGSN sends an update PDP context request message tothe GGSN;

step S1012: the GGSN returns an update PDP context response message tothe 2G SGSN;

step S1013: the GGSN forwards the buffered forwarded data packet to the2G SGSN;

step S1014: the 2G SGSN returns a routing area update accept message tothe MS;

step S1015: the MS returns a routing area update complete message to the2G SGSN.

In order to enhance its competitive advantages in the future, the 3GPPis studying new evolved network architecture, including SystemArchitecture Evolution (SAE) and Long Term Evolution (LTE) accessnetwork. The evolved access network is known as E-UTRAN, networkarchitecture of an evolved packet core network, illustrated as in FIG.11, includes a Mobility Management Entity (MME), a User Plane Entity(UPE), and an Inter Access System Anchor (IASA). The MME performsmobility management in the control plane, including user context andmobility status management, user temporary identity identifierassignment and so forth, corresponding to the control plane of an SGSNinside GPRS/UMTS; the UPE is used to initiate paging for downlink datain idle state, manages and stores IP bearer parameters and routinginformation inside the network and so forth, corresponding to the dataplane of an SGSN and a GGSN in GPRS/UMTS; the IASA is an anchor in theuser plane between different systems. A Policy and Charging RuleFunction (PCRF) entity is used for policy control decision and chargingcontrol of data flow. A Home Subscriber Server (HSS) is used to storeuser subscription information.

For the SAE system, if the MME and the UPE are separate, and the UPE andthe 3GPP Anchor are in a same entity, the systematic architecture issimilar to the architecture in the direct-tunnel mechanism where the MMEcorresponds to an SGSN, and the UPE/3GPP Anchor (referred to as UPEhereinafter) corresponds to a GGSN. Therefore the data forwardingprocessing method stated above can be used for data forwarding when ahandover or change between a GERAN/UTRAN system and an SAE system takesplace.

When a handover or change from a GERAN system to an SAE system takesplace, the MME and the UPE (user plane anchor of the GERAN/UTRAN and theSAE) exchange messages including a forward data request message and aforward data response message, to obtain a data forwarding tunnelidentifier of the UPE, and inform the 2G SGSN of the data forwardingtunnel identifier of the UPE. The 2G SGSN forwards a data packet to theUPE; the UPE buffers the forwarded data packet and forwards the bufferedforwarded data packet to the evolved access network on completion ofupdate of user plane routing.

When a handover or change from an SAE system to a GERAN system takesplace, the MME and the UPE exchange messages including a forward datarequest message and a forward data response message, to obtain a dataforwarding tunnel identifier of the UPE, and inform the evolved accessnetwork of the data forwarding tunnel identifier of the UPE. The evolvedaccess network forwards a data packet to the UPE; the UPE buffers theforwarded data packet and forwards the buffered forwarded data packet tothe 2G SGSN on completion of update of user plane routing.

When a handover or change from a UTRAN system to an SAE system takesplace, the 3G SGSN and the UPE exchange messages including a forwarddata request message and a forward data response message, to obtain adata forwarding tunnel identifier of the UPE, and inform the source RNCof the data forwarding tunnel identifier of the UPE. The source RNCforwards a data packet to the UPE; the UPE buffers the forwarded datapacket and forwards the buffered forwarded data packet to the evolvedaccess network on completion of update of user plane routing.

When a handover or change from an SAE system to a UTRAN system takesplace, the MME and the UPE exchange messages including a forward datarequest message and a forward data response message, to obtain a dataforwarding tunnel identifier of the UPE, and inform the evolved accessnetwork of the data forwarding tunnel identifier of the UPE. The evolvedaccess network forwards a data packet to the UPE; the UPE buffers theforwarded data packet and forwards the buffered forwarded data packet tothe target RNC on completion of update of user plane routing.

Now refer to FIGS. 12 to 15. Another data processing method embodimentprovided by the present invention is described.

With reference to FIG. 12, a data processing method when a handover froma GERAN to a UTRAN takes place includes:

step 1201: a source BSS decides to initiate a handover;

step 1202: the source BSS sends a handover request message to an oldSGSN, i.e. 2G SGSN;

step 1203: the 2G SGSN sends a forward relocation request message to anew SGSN, i.e. 3G SGSN;

step 1204: the 3G SGSN builds a relocation request message and sends themessage to a target RNC;

step 1205: the target RNC sends relocation request acknowledge messageto the 3G SGSN;

step 1206: the 3G SGSN sends a forward data request message to a GGSN,to request the GGSN to assign a data forwarding tunnel for dataforwarding, an identifier of a GTP tunnel of the target RNC side iscarried in the message, subsequently the GGSN will forward data of alossless service to the GTP tunnel;

step 1207: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel, and sends to the 3G SGSN in the response message;

step 1208: the 3G SGSN sends a forward relocation response message tothe 2G SGSN, a data forwarding tunnel identifier carried in the messageis the data forwarding tunnel identifier of the GGSN;

step 1209: the 2G SGSN receives a data packet from the GGSN, and sendsthe data packet to an MS via the source BSS;

step 1210: for data of a lossless service, the 2G SGSN forwards the datapacket to the GGSN according to the data forwarding tunnel identifiercarried in the forward relocation response message sent by the 3G SGSN,the GGSN forwards the data packet forwarded by the 2G SGSN to the targetRNC on receipt of the data packet;

step 1211: the 2G SGSN sends a handover request acknowledge message tothe source BSS;

step S1212: the MS sends a handover to UTRAN complete message to thetarget RNC;

step S1213: the target RNC sends a relocation complete message to the 3GSGSN;

step S1214: the 3G SGSN sends an update context request message to theGGSN;

step S1215: the GGSN returns an update context response message to the3G SGSN.

With reference to FIG. 13, a data processing method when a handover froma UTRAN to a GERAN takes place includes:

step S1301: a source RNC decides to initiate a handover;

step S1302: the source RNC sends a relocation request message to an oldSGSN, i.e. 3G SGSN;

step S1303: the 3G SGSN sends a forward relocation request message to anew SGSN, i.e. 2G SGSN;

step S1304: the 2G SGSN builds a handover request message, and sends themessage to a target BSS;

step S1305: the target BSS sends a handover request acknowledged messageto the 2G SGSN;

step S1306: the 2G SGSN sends a forward relocation response message tothe 3G SGSN;

step S1307: the 3G SGSN sends a forward data request to a GGSN, torequest the GGSN to assign a data forwarding tunnel for data forwarding,an identifier of a data forwarding tunnel of the 2G SGSN is carried inthe message, subsequently the GGSN will forward data of a losslessservice to the data forwarding tunnel;

step S1308: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel and carries the data forwarding tunnel identifier in the responsemessage to the 3G SGSN;

step S1309: the 3G SGSN receives a data packet from the GGSN, and sendsthe data packet to an MS via the source RNC;

step S1310: the 3G SGSN sends a relocation command message to the sourceRNC, a data forwarding tunnel identifier carried in the message is thedata forwarding tunnel identifier of the GGSN;

step S1311: for data of a lossless service, the source RNC forwards thedata packet to the GGSN according to the data forwarding tunnelidentifier carried in the relocation command message sent by the 3GSGSN, the GGSN forwards the data packet forwarded by the source RNC tothe 2G SGSN on receipt of the data packet, the 2G SGSN forwards the datapacket to the target BSS;

step S1312: the target BSS sends a handover complete message to the 2GSGSN;

step S1313: the 2G SGSN sends an update context request message to theGGSN;

step S1314: the GGSN returns an update context response message to the2G SGSN.

With reference to FIG. 14, a data processing method when a change from aGERAN to a UTRAN takes place includes.

step S1401: an MS decides to initiate an intersystem change;

step S1402: the MS sends a routing area update request message to a newSGSN, i.e. 3G SGSN;

step S1403: the 3G SGSN sends an SGSN context request message to an oldSGSN, i.e. 2G SGSN, to obtain user context;

step S1404: the 2G SGSN returns SGSN context response message to the 3GSGSN, and carries the user context information in the message;

step 1405: RAB assignment procedure is performed between the 3G SGSN andan RNC, thereby establishing RAB;

step S1406: the 3G SGSN sends an update PDP context request message to aGGSN, to request to change user plane routing from the GGSN to the 3GSGSN;

step S1407: the GGSN returns an update PDP context response to the 3GSGSN;

step S1408: the 3G SGSN sends a forward data request message to theGGSN, to request the GGSN to assign a data forwarding tunnel for dataforwarding, an identifier of a GTP tunnel of the target RNC side iscarried in the message, subsequently the GGSN will forward data of alossless service to the GTP tunnel;

step S1409: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel, and carries the data forwarding tunnel identifier in theresponse message to the 3G SGSN;

step S1410: the 3G SGSN sends an SGSN context acknowledge message to the2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive datapackets, a data forwarding tunnel identifier carried in the message isthe data forwarding tunnel identifier of the GGSN;

step S1411: the 2G SGSN duplicates a buffered data packet and forwardsto the GGSN according to the data forwarding tunnel identifier carriedin the SGSN context acknowledge message sent by the 3G SGSN, the GGSNforwards the data packet forwarded by the 2G SGSN to the target RNC onreceipt of the data packet;

step S1412: the 3G SGSN returns a routing area update accept message tothe MS;

step S1413: the MS returns a routing area update complete message to the3G SGSN;

step S1414: the 3G SGSN sends an update context request message to theGGSN, to change a downlink GTP tunnel identifier of user context in theGGSN to the GTP tunnel identifier of the RNC;

step S1415: the GGSN returns an update context response message to the3G SGSN.

With reference to FIG. 15, a data processing method when a change from aUTRAN to a GERAN takes place includes:

step S1501: an MS decides to initiate an intersystem change;

step S1502: the MS sends a routing area update request message to a newSGSN, i.e. 2G SGSN;

step S1503: the 2G SGSN sends an SGSN context request message to an oldSGSN, i.e. 3G SGSN, to obtain user context;

step S1504: the 3G SGSN sends an SRNS context request message to asource RNC;

step S1505: the source RNC returns an SRNS context response message tothe 3G SGSN, stops sending downlink data to the MS, and buffers thedata;

step S1506: the 3G SGSN returns an SGSN context response message to the2G SGSN, and carries the user context information in the message;

step S1507: the 2G SGSN sends an SGSN context acknowledge message to the3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive datapackets;

step S1508: the 3G SGSN sends a forward data request to a GGSN, torequest the GGSN to assign a data forwarding tunnel for data forwarding,an identifier of a data forwarding tunnel of the 2G SGSN is carried inthe message, subsequently the GGSN will forward data of a losslessservice to the data forwarding channel;

step S1509: the GGSN returns a forward data response message to the 3GSGSN, assigns a data forwarding tunnel identifier to the data forwardingtunnel, and carries the data forwarding tunnel identifier in theresponse message to the 3G SGSN;

step S1510: the 3G SGSN sends an SRNS data forward command to the sourceRNC, a data forwarding tunnel identifier carried in the message is thedata forwarding tunnel identifier of the GGSN, the source RNC duplicatesa buffered data packet and forwards to the GGSN, the GGSN forwards thedata packet forwarded by the source RNC to the 2G SGSN on receipt of thedata packet;

step S1511: the 2G SGSN sends an update PDP context request message tothe GGSN;

step S1512: the GGSN returns an update PDP context response message tothe 2G SGSN;

step S1513: the 2G SGSN returns a routing area update accept message tothe MS;

step S1514: the MS returns a routing area update complete message to the2G SGSN.

The data forwarding processing method stated above can be used for dataforwarding when a handover or change between a GERAN/UTRAN system and anSAE system takes place.

When a handover or change from a GERAN system to an SAE system takesplace, the MME and the UPE exchange messages including a forward datarequest message and a forward data response message, to obtain a dataforwarding tunnel identifier of the UPE. Meanwhile the MME informs theUPE of a tunnel identifier of the access network side, and informs the2G SGSN of the data forwarding tunnel identifier of the UPE. The 2G SGSNforwards a data packet to the UPE, and the UPE further forwards the datapacket to the evolved access network.

When a handover or change from an SAE system to a GERAN system takesplace, the MME and the UPE exchange messages including a forward datarequest message and a forward data response message, to obtain a dataforwarding tunnel identifier of the UPE. Meanwhile, the MME informs theUPE of a tunnel identifier of the 2G SGSN, and then informs the evolvedaccess network of the data forwarding tunnel identifier of the UPE. Theevolved access network forwards a data packet to the UPE, and the UPEfurther forwards the data packet the 2G SGSN.

When a handover or change from a UTRAN system to an SAE system takesplace, the 3G SGSN and the UPE exchange messages including a forwarddata request message and a forward data response message, to obtain adata forwarding tunnel identifier of the UPE Meanwhile, the UPE isinformed of a tunnel identifier of the evolved access network side. Thenthe 3G SGSN informs the source RNC of the data forwarding tunnelidentifier of the UPE. The source RNC forwards a data packet to the UPE,and the UPE further forwards the data packet to the evolved accessnetwork.

When a handover or change from an SAE system to a UTRAN system takesplace, the MME and the UPE exchange messages including a forward datarequest message and a forward data response message, to obtain a dataforwarding tunnel identifier of the UPE. Meanwhile the MME informs theUPE of a tunnel identifier of the target RNC and then informs theevolved access network of the data forwarding tunnel identifier of theUPE. The evolved access network forwards a data packet to the UPE, andthe UPE further forwards the data packet to the target RNC.

Another data processing method when an intersystem handover or changetakes place is provided with an embodiment of the present invention,including:

A user plane anchor network element sends data to a source dataforwarding network element and a target side processing network elementon receipt of an instruction. The instruction may be a bicast commandinstruction instructing the user plane anchor network element to senddata to the source data forwarding network element and the target sideprocessing network element. On completion of update of user planerouting, the user plane anchor network element stops bicasting and sendsdata to the target side processing network element only.

With reference to FIG. 16, a data processing method when a handover froma GERAN to a UTRAN takes place includes:

step 1601: a source BSS decides to initiate a handover;

step 1602: the source BSS sends a handover request message to an oldSGSN, i.e. 2G SGSN;

step 1603: the 2G SGSN sends a forward relocation request message to anew SGSN, i.e. 3G SGSN;

step 1604: the 3G SGSN builds a relocation request message and sends themessage to a target RNC;

step 1605: the target RNC sends relocation request acknowledge messageto the 3G SGSN;

step 1606: the 3G SGSN sends a forward relocation response message tothe 2G SGSN, an indication is carried in the message to instruct the 2GSGSN not to perform data forwarding;

step 1607: the 3G SGSN sends a bicast command message to a GGSN,instructing the GGSN to send data to the 2G SGSN and the target RNC, aGTP tunnel identifier of the target RNC is carried in the message;

step 1608: the GGSN sends a downlink data packet to the 2G SGSN and thetarget RNC;

step 1609: the 2G SGSN sends a handover request acknowledge message tothe source BSS;

step 1610: an MS sends a handover to UTRAN complete message to thetarget RNC;

step 1611: the target RNC sends a relocation complete message to the 3GSGSN;

step 1612: a process of PDP context update is performed between the 3GSGSN and the GGSN, which changes a downlink GTP tunnel identifier ofuser in the GGSN to the GTP tunnel identifier of the target RNC, theGGSN stops data bicasting in the process;

step 1613: the GGSN sends a downlink data packet to the target RNC.

With reference to FIG. 17, a data processing method when a handover froma UTRAN to a GERAN takes place includes:

step S1701: a source RNC decides to initiate a handover;

step S1702: the source RNC sends a relocation request message to an oldSGSN, i.e. 3G SGSN;

step S1703: the 3G SGSN sends a forward relocation request message to anew SGSN, i.e. 2G SGSN;

step S1704: the 2G SGSN builds a handover request message, and sends themessage to a target BSS;

step S1705: the target BSS sends a handover request acknowledged messageto the 2G SGSN;

step S1706: the 2G SGSN sends a forward relocation response message tothe 3G SGSN;

step S1707: the 3G SGSN sends a bicast command message to a GGSN,instructing the GGSN to send data to the source RNC and the 2G SGSN, aGTP tunnel identifier of the 2G SGSN is carried in the message;

step S1708: the GGSN sends a downlink data pack to the source RNC andthe 2G SGSN;

step S1709: the 3G SGSN sends a relocation command message to the sourceRNC, an indication is carried in the message to instruct the source RNCnot to perform data forwarding;

step S1710: the target BSS sends a handover complete message to the 2GSGSN;

step S1711: a process of PDP context update is performed between the 2GSGSN and the GGSN, which changes a downlink GTP tunnel identifier ofuser in the GGSN to the GTP tunnel identifier of the 2G SGSN, the GGSNstops data bicasting in the process;

step S1712: the GGSN sends a downlink data packet to the 2G SGSN, the 2GSGSN sends the downlink data packet to the target BSS.

With reference to FIG. 18, a data processing method when a change from aGERAN to a UTRAN takes place includes.

step S1801: an MS decides to initiate an intersystem change;

step S1802: the MS sends a routing area update request message to a newSGSN, i.e. 3G SGSN;

step S1803: the 3G SGSN sends an SGSN context request message to an oldSGSN, i.e. 2G SGSN, to obtain user context;

step S1804: the 2G SGSN returns an SGSN context response message to the3G SGSN, and carries the user context information in the message;

step 1805: RAB assignment procedure is performed between the 3G SGSN andan RNC, thereby establishing RAB;

step S1806: the 3G SGSN sends an SGSN context acknowledge message to the2G SGSN, an indication is carried in the message to instruct the 2G SGSNnot to perform data forwarding;

step S1807: the 3G SGSN sends a bicast command message to the GGSN,instructing the GGSN to send data to the 2G SGSN and a target RNC, a GTPtunnel identifier of the target RNC is carried in the message;

step S1808: the GGSN sends a downlink data packet to the 2G SGSN and thetarget RNC;

step S1809: the 3G SGSN returns a routing area update accept message tothe MS;

step S1810: the MS returns a routing area update complete message to the3G SGSN;

step S1811: a process of PDP context update is performed between the 3GSGSN and the GGSN, which changes a downlink GTP tunnel identifier ofuser in the GGSN to the GTP tunnel identifier of the target RNC, theGGSN stops data bicasting in the process;

step S1812: the GGSN sends a downlink data packet to the target RNC.

With reference to FIG. 19, a data processing method when a change from aUTRAN to a GERAN takes place includes:

step S1901: an MS decides to initiate an intersystem change;

step S1902: the MS sends a routing area update request message to a newSGSN, i.e. 2G SGSN;

step S1903: the 2G SGSN sends an SGSN context request message to an oldSGSN, i.e. 3G SGSN, to obtain user context;

step S1904: the 3G SGSN sends an SRNS context request message to asource RNC;

step S1905: the source RNC returns an SRNS context response message tothe 3G SGSN, stops sending downlink data to the MS, and buffers thedata;

step S1906: the 3G SGSN returns an SGSN context response message to the2G SGSN, and carries the user context information in the message;

step S1907: the 2G SGSN sends an SGSN context acknowledge message to the3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive datapackets;

step S1908: the 3G SGSN sends a bicast command message to the GGSN,instructing the GGSN to send data to the source RNC and the 2G SGSN, aGTP tunnel identifier of the 2G SGSN is carried in the message;

step S1909: the GGSN sends a downlink data packet to the source RNC andthe 2G SGSN;

step S1910: a process of PDP context update is performed between the 2GSGSN and the GGSN, which changes a downlink GTP tunnel identifier ofuser in the GGSN to the GTP tunnel identifier of the 2G SGSN, the GGSNstops data bicasting in the process;

step S1911: the GGSN sends a downlink data packet to the 2G SGSN, the2GSN sends the downlink data packet to the MS;

step S1912: the 2G SGSN returns a routing area update accept message tothe MS;

step S1913: the MS returns a routing area update complete message to the2G SGSN.

The data forwarding processing method stated above can be used for dataforwarding when a handover or change between a GERAN/UTRAN system and anSAE system takes place.

When a handover or change from a GERAN system to an SAE system takesplace, the MME sends a bicast command message to the UPE, instructingthe UPE to send data to the 2G SGSN and the LTE. The UPE sends adownlink data packet to the 2G SGSN and the LTE. On completion of updateof user plane routing, the UPE stops downlink data packet bicasting, andsends a downlink data packet to the LTE only.

When a handover or change from an SAE system to a GERAN system takesplace, the MME sends a bicast command message to the UPE, instructingthe UPE to send data to the LTE and the 2G SGSN. The UPE sends adownlink data packet to the LTE and the 2G SGSN. On completion of updateof user plane routing, the UPE stops downlink data packet bicasting, andsends a downlink data packet to the 2G SGSN only.

When a handover or change from a UTRAN system to an SAE system takesplace, the MME sends a bicast command message to the UPE, instructingthe UPE to send data to the source RNC and the LTE. The UPE sends adownlink data packet to the source RNC and the LTE. On completion ofupdate of user plane routing, the UPE stops downlink data packetbicasting, and sends a downlink data packet to the LTE only.

When a handover or change from an SAE system to a UTRAN system takesplace, the MME sends a bicast command message to the UPE, instructingthe UPE to send data to the LTE and the target RNC. The UPE sends adownlink data packet to the LTE and the target RNC. On completion ofupdate of user plane routing, the UPE stops downlink data packetbicasting, and sends a downlink data packet to the target RNC only.

With reference to FIG. 20, a data processing system is provided in anembodiment of the present invention, including a source data forwardingnetwork element, a target side processing network element and a userplane anchor network element, wherein the user plane anchor networkelement is provided with a receipt unit adapted to receive dataforwarded by the source data forwarding network element, and a sendingunit adapted to forward the received data to the target side processingnetwork element.

In an embodiment of the present invention, the source data forwardingnetwork element is a 2G Serving GPRS Support Node (SGSN), the user planeanchor network element is a Gateway GPRS Support Node (GGSN), and thetarget side processing network element is a target Radio NetworkController (RNC).

In another embodiment of the present invention, the source dataforwarding network element is a source RNC, the user plane anchornetwork element is a GGSN, and the target side processing networkelement is a 2G SGSN.

The data processing system further includes: a tunnel identifieracquisition unit, arranged in the 3G SGSN and adapted to acquire a dataforwarding tunnel identifier of the GGSN; and a tunnel identifiersending unit, adapted to send a GTP tunnel identifier of the target RNCside to the GGSN.

The data processing system further includes: a data packet buffer unit,arranged in the GGSN and adapted to receive a data packet forwarded bythe 2G SGSN and buffer a data packet forwarded by the target sideprocessing network element; and a data packet sending unit, adapted tosend the buffered data packet.

In the direct-tunnel mechanism, when a handover or change between aGERAN and a UTRAN takes place, data forwarded by the source dataforwarding network element can be buffered in the data packet bufferunit, which forwards the buffered data packet to the target RNC when theGGSN completes update of user plane routing or the GGSN receives anupdate PDP context request message sent by the 3G SGSN. Also, the dataforwarded by the source data forwarding network element can be forwardeddirectly to the target side processing network element.

When an intersystem handover or change takes place, interactions amongthe source data forwarding network element, target side processingnetwork element and the user plane anchor network element are same orsimilar to the steps described in the above embodiments.

When the user plane anchor network element receive an instructivemessage and sends data to the source data forwarding network elementand/or the target side processing network element, the user plane anchornetwork element updates user plane routing and only sends the data tothe target side processing network element as instructed in the messageaccording to the updated user plane routing.

Those skilled in the art should understand that each step in the aboveembodiments can be implemented by a program instructing relatedhardware. The program can be stored in computer readable storage mediumsuch as ROM/RAM, magnetic disk and optical discs. Alternatively, theembodiments can be implemented with respective integrated circuitmodules, or the steps of which can be made into separate integratedcircuit modules. Therefore, the present invention is not limited to anyparticular hardware or software combination.

As can be seen from the above embodiments, with the data processingmethods in the direct-tunnel mechanism when a handover or change betweena GERAN and a UTRAN takes place, a GGSN can buffer data forwarded by asource data forwarding network element and then send the data to atarget side processing network element, alternatively, the GGSN can sendthe data forwarded by the source data forwarding network elementdirectly to the target side processing network element. The problem thatthe data processing method in the conventional art is not applicable inthe direct-tunnel mechanism is solved. Handover or change between aGERAN and a UTRAN in the direct-tunnel mechanism does not affectforwarding of service data.

Exemplary embodiments of the present invention are described. It shouldbe noted that those skilled in the art may make various alternations ormodifications without departing from the principle of the presentinvention. The alternations and modifications should be covered withinthe scope of the present invention.

What is claimed is:
 1. A method in a handover between two Long TermEvolution (LTE) access networks, the method comprising: informing, by aMobility Management Entity (MME), a User Plane Entity (UPE) of a dataforwarding tunnel identifier of a target LTE access network; obtaining,by the MME, a data forwarding tunnel identifier of the UPE; informing,by the MME, a source LTE access network of the data forwarding tunnelidentifier of the UPE; transmitting, by the source LTE access network,data to the UPE using the data forwarding tunnel identifier of the UPE;and transmitting, by the UPE, the data to the target LTE access network.2. The method according to claim 1, wherein obtaining the dataforwarding tunnel identifier of the UPE comprises: sending, by the MME,a forward data request to the UPE; and receiving, by the MME, from theUPE a forward data response carrying the data forward tunnel identifierof the UPE.
 3. The method according to claim 1, wherein the dataforwarding tunnel identifier of the target LTE access network comprisesan address and a Tunnel End Point Identifier (TEID) of the target LTEaccess network, and the data forwarding tunnel identifier of the UPEcomprises an address and a TEID of the UPE.
 4. A communication systemcomprising: a Mobility Management Entity (MME); a User Plane Entity(UPE); and a source Long Term Evolution (LTE) access network, whereinthe MME is configured to inform the UPE of a data forwarding tunnelidentifier of a target LTE access network, obtain a data forwardingtunnel identifier of the UPE, and inform the source LTE access networkof the data forwarding tunnel identifier of the UPE; wherein the sourceLTE access network is configured to transmit data to the UPE using thedata forwarding tunnel identifier of the UPE; and wherein the UPE isconfigured to transmit the data to the target LTE access network usingthe data forwarding tunnel identifier of the target LTE access network.5. The communication system according to claim 4, wherein the MME isconfigured to: send a forward data request to the UPE; and receive fromthe UPE a forward data response carrying the data forward tunnelidentifier of the UPE.
 6. The communication system according to claim 4,wherein the data forwarding tunnel identifier of the target LTE accessnetwork comprises an address and a Tunnel End Point Identifier (TEID) ofthe target LTE access network, and the data forwarding tunnel identifierof the UPE comprises an address and a TEID of the UPE.